The field of the invention relates generally to semiconductor devices, and more specifically, to sputtering films on semiconductor devices.
In forming semiconductor devices, thin films (10-3000 Angstroms) are often deposited using physical vapor deposition (PVD) or sputtering in a sputtering chamber. Traditional sputtering uses an argon atom ionized by a high power (approximately 500 W-10,000 W) and a low pressure (approximately 0.5-30 mTorr) to bombard a target. Released by the bombardment of the target with argon, a neutral target atom travels to a semiconductor wafer and forms the thin film in conjunction with other atoms from the target and/or other gases that may be present in the sputtering chamber. As device dimensions (particularly the width of vias,) shrink, the ability to sputter neutral atoms into narrow vias using traditional sputtering is difficult because more of the neutral atoms deposit at the top of the vias than at the sidewalls and bottom and thus the opening of the vias can close without suitable deposition within the via. Even if the opening isn""t closed, the uniformity of the thin film in the vias is poor.
By ionizing the atoms released from the target as done in ionized PVD (iPVD), another type of sputtering, thin film deposition within narrow vias is improved by the ability to control the path of the ionized atoms released from the target by electric and magnetic fields. Thus, controlling where the atoms deposit on the semiconductor wafer. One approach uses two circular electromagnetic rings outside the sputtering chamber, one above and one below wafer level, to control electric and magnetic fields and, hence, the path of the released atoms from the target to the semiconductor wafer. Due to the presence of features in the sputtering chamber, such as gas inlets, a pumping port, and a slit valve, the two circular magnetic rings do not produce uniform electric fields within the chamber. Hence, while uniformity on a local scale (e.g. within vias) is improved, uniformity of the thin film across the semiconductor wafer is poor, which results in yield loss and increases manufacturing costs. Therefore, a need exits to improve uniformity of the thin film across the semiconductor wafer.